The present invention relates to an apparatus for both etching and coating a specimen prior to analysis, and more particularly to an ion beam etching and sputter coating system for the preparation of sample specimens to be analyzed in a microscope.
Ion milling systems are used extensively for etching, milling, cutting, and cleaning samples of various materials such as ceramics, semiconductors, metals, and combinations thereof to make possible and/or enhance certain features for analysis in a microscope, typically analysis with an electron or optical microscope. Many of these samples, particularly samples of electrically insulating materials, are coated after cleaning or etching and prior to examination in an electron or optical microscope to prevent charging effects. Certain coatings also have the effect of increasing the secondary electron yield from almost all types of material.
Typically for etching and coating, the samples to be studied are first mounted to a sample holder for the purpose of mechanically polishing one or more surfaces until such surfaces are flat, parallel, and scratch free. The polished sample is then removed from the polishing holder, mounted to a second holder, and placed into an ion milling device for etching. In the ion mill, the sample is positioned in the path of one or more ion beams and etched at a relatively steep angle between the incident beam(s) and the sample surface.
Once etching has been completed, the sample may require remounting to a third holder to enable installation into a separate device for the purpose of depositing a conductive coating thereon. Previously, such coatings were applied by such techniques as thermal evaporation, arc discharge, and diode, magnetron, or RF sputtering. More recently, the coatings have been applied by sputter coating in a vacuum using ion beam techniques.
After coating, the sample may be mounted to a final stub or holder designed for use in a specific microscope, for example a transmission electron microscope, a scanning electron microscope, or even a light microscope. Thus, the current techniques for sample preparation require that the samples be handled multiple times and transferred among several instruments and vacuum systems. These techniques expose the samples to potential damage and/or contamination of the sample surface.
Accordingly, there is a need in the art for a process and system which minimizes sample handling and exposure to potential damage and/or contamination.